But the office cautioned in a statement that seismic activity at the volcano, which has been hit by thousands of earthquakes over the past week, was not slowing and an eruption remained a possibility in coming days.

There are fears that if the volcano erupts it could cause disruption similar to that seen in 2010 when an ash cloud from the Eyjafjallajokul brought Manchester Airport to a standstill.

Iceland had raised the alert for aviation yesterday to red, the highest level on a five-point scale, warning that an ash-emitting eruption could be imminent.

After the alert was lowered, aviation authorities lifted a no-fly zone that had been imposed for 100 nautical miles by 140 nautical miles (185 kilometres by 260 kilometres) around the volcano.

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The UK's air traffic control organisation NATS said it was monitoring what it called a "dynamic situation" but was expecting normal operations today.

The 2010 eruption of Eyjafjallajokul caused a week of international aviation chaos, with more than 100,000 flights cancelled.

Hundreds of thousands of people alone at Manchester faced disruption when all flights were grounded around the UK.

Aviation officials closed Europe's air space for five days out of fear that volcanic ash could harm jet engines.

Any new eruption would be likely to be less disruptive. European aviation authorities have changed their policy, giving airlines detailed information about the location and density of ash clouds but leaving decisions to airlines and national regulators.